1. Field of the Invention
The present invention relates to hybrid water dispersions, (poly(ethylene) (meth)acrylic acid copolymer composite latex emulsions, hybrid (poly)ethylene (meth)acrylic acid organsilane composite latex emulsions, coating compositions formed from the foregoing, methods of coating substrates with the foregoing, and substrates coated with the foregoing.
2. Description of Related Art
Coating compositions formed from epoxy resins have been used to coat packaging and containers for foods and beverages. Although the weight of scientific evidence, as interpreted by the major global regulatory food safety agencies in the US, Canada, Europe, and Japan, shows that the levels of bisphenol A consumers are exposed to with current commercial epoxy based coatings is safe, some consumers and brand owners continue to express concern, and a coating that does not contain bisphenol A or any other endocrine disruptor is desirable. There is also a desire to eliminate surfactants from such coating compositions, because the surfactants could in theory dissolve in the beverages.
Commonly-owned WO 2010/97353 describes the preparation of latex emulsions used in coating compositions useful for packaging coating beverage inside spray applications. Commonly-owned patent publication WO 2012/089747 describes the preparation of core-shell latex emulsions by for beverage end applications. Such latex emulsions have not achieved the performance of epoxy based coatings and have not been successfully used on a commercial basis in food and beverage coating compositions.
High acid content, high melt index (poly)ethylene (meth)acrylic acid copolymers are dispersible in alkali aqueous dispersions under proper reaction conditions. Such aqueous dispersions are widely used in adhesives, personal care applications and paper coating applications. U.S. Pat. No. 7,803,865 describes a process to prepare such aqueous dispersions in an extruder. However, (poly)ethylene (meth)acrylic acid copolymer dispersions are hydrophilic and have poor chemical resistance and poor blush resistance. Crosslinkers (such as melamine formaldehyde, urea formaldehyde, phenol formaldehyde, alkali metal hydroxides, zinc/zirconium complexes and epoxy resins) have been used to improve chemical and blush resistance, but these crosslinkers do not produce a coating with sufficient chemical and blush resistance required for many packaging coating applications.
There is a need to produce coating compositions that do not contain bisphenol A or are substantially free of bisphenol A. There is also a need to produce coating compositions that do not contain phenolic resins or are substantially free of phenolic resins and do not contain surfactants in order to reduce migration of the coating composition into food and beverages.